Testing a device, or integrated circuit, is typically performed by test equipment. Testing may include measuring signals output from the integrated circuit. However, some integrated circuits may output a relatively small-swing differential signal that requires expensive test equipment for measuring the relatively small signal.
In order to avoid using the expensive testing equipment, an integrated circuit may be designed to include dedicated test output circuits coupled to test pads or contacts that output a larger single-ended signal. However, using dedicated test output circuits and pads increase circuit complexity, circuit area and the use of limited pad resources. Further, the increased parasitic capacitance contribution from the additional test output circuit would degrade input signal high frequency components during typical or normal operations.
Also during a wafer sort of semiconductor device manufacturing process, minimizing the number of test probes used to input and measure an output signal reduces test complexity and costs associated with additional probes.
Therefore, it is desirable to provide an integrated circuit having an output circuit for a typical operation as well as for a testing operation without requiring the use of expensive test equipment for measuring a small-swing differential signal.